This invention pertains to separating fine particles from ore minerals, mine tailings and the like and, more particularly, to recovering valuable fine particles of minerals and metals by centrifuging and froth flotation.
Centrifuges and centrifugal separators are commonly used to separate fluid mixtures by centrifugal force into higher density and lower density fractions in order to separate one material from another material. Conventional centrifuges and centrifugal separators have met with varying degrees of success depending on the materials being separated. Many conventional centrifuges, however, are expensive, have high operational energy requirements, create excessive turbulence, cause high pressure discharges, and can require complex auxiliary equipment, such as slurry accelerators.
Another type of separating process is froth flotation. In conventional (traditional) froth flotation, an input stream, such as a mineral slurry, is combined and commingled with an airstream. Conventional froth flotation separates materials primarily by the attachment of air bubbles and mineral particles. Air bubbles attach with hydrophobic material from the input stream float to the surface as a froth, while hydrophillic material unable to attache with bubbles sinks to the bottom. The froth is skimmed off the surface.
Froth flotation is a known process for the separation of finely ground minerals from slurries or suspensions in a liquid, usually water. The particles desired to remove from the slurry can be treated with chemical reagents to render them hydrophobic or water repellent, and a gas, usually air, is introduced into the slurry in the form of small bubbles. The air bubbles contact with the hydrophobic particles and carry them to the surface of the slurry to form a stabilized froth. The froth containing the floated particles is then removed as the concentrate or float product, while any hydrophilic particles remain submerged in the slurry and then are discharged. Conventional froth flotation has met with varying degrees of success.
Precious metals and valuable minerals are mined from ores and mineral deposits throughout the world for a variety of uses. It is important to maximize recovery of precious metals and valuable minerals during mining operation from an economic standpoint and operate the mine in an environmentally responsible and safe manner. Mining operations produce huge ponds of tailings containing very fine particles (fines) of precious metals and valuable minerals which are generally not recoverable by conventional, traditional froth flotation, and other conventional separating techniques.
Many industries use precious metals and valuable minerals for different purposes. For example, oil refineries and petrochemicals plants use platinum, nickel, antimony, etc. for catalysts to convert oil into fractions which are useful to produce gasoline and other fuels, as well as to produce chemicals for textiles and plastics. Once the catalysts have been used, precious metals can often be recovered or regenerated for further use. Numerous methods have been used in an effort to reclaim precious metals. In reclamation, vast reservoirs of tailings containing fine particles (fines) of precious metals are often produced but the valuable fines are generally unable to be reclaimed by conventional, froth flotation and other conventional separating techniques.
A centrifugal flotation cell has been developed as described in Campbell U.S. Pat. No. 4,874,357 which combines centrifuging and froth flotation to recover a greater amount of valuable fines. While this provides a very useful apparatus and method, it is desirable to provide an improved centrifugal flotation cell and process which are faster, more economical and recover greater quantities of valuable fines, as well as which overcome most, if not all, of the preceding problems.